In the winter, I'll walk home in -30 during a blizzard, 3-foot snowdrifts, with a huge backpack of groceries. It's like being on the planet Hoth, fucking insanely difficult, and I'll rage out loud right back at the storm, "C'mon! You can do worse than that, you big sissy!!" It feels so amazing to finally get home--like I've really walked the gauntlet and the reward is being warm, exhausted, and still alive. Coworkers think I'm completely nuts for doing this, but I love it. ...And they all pay for gym memberships.
Hmmm.... Come to think of it, I do the same thing in the summer during a heatwave. Get home completely drenched with sweat and jump in a cool shower ASAP.